Bruk av MRI og NMR-spektroskopi for å karakterisere fukteigenskapar ved ulike magnetiske feltstyrkar

In this thesis, use of Nuclear Magnetic Resonance (NMR)-spectroscopy and Magnetic Resonance Imaging (MRI) is used to characterize pore size and wettability in a porous medium. NMR is a method that is increasingly used in the petroleum industry, due to its non-destructive and non-invasive method. Two Edward Limestones were measured at 200 MHz Biospec MRI-scanner at 22°C, and at 12 MHz Maran Ultra DRX spectrometer at 35°C. The rock cores were measured at 100% water saturated, irreducible water saturation and residual oil saturation. The rock cores were then aged and measured again at irreducible water saturation and residual oil saturation. At high magnetic field (200 MHz) T_2-mapping, T_2 average and T_1 mapping were measured. At low field (12 MHz) the T_2 average were measured, in addition to correlation with longitudinal relaxation (T_1)-transverse relaxation (T_2), pore size-T_2, and internal gradient (G_0)-T_2. The rock cores used are heterogenic and the permeability and porosity will vary through the core. They are original water wet, where water has the strongest connection (adhesive force) to the surface. From the correlation with T_2 and internal gradient/pore size, it is possible to observe that the smallest pores are mostly occupied by water, while water and oil occupies the bigger pores. After aging, one of the rock cores is neutral wet, while the other is oil wet, thus giving the oil stronger binding to the pore surface. From the T_1 measured at high magnetic field (200 MHz) it is possible to observe changes in wettability and different saturation states. At high field T_2 will be affected by the susceptibility differences in the magnetic field, and the T_2 values will be inconclusive. The susceptibility difference is smaller at lower magnetic field (12 MHz) and here the T_2-values can be used to determine the saturation and wettability. T_1 is a less sensitive method and will not be a good parameter at low field. It is not possible to separate the oil and water signal from the T_1 measurements on either high or low magnetic fields. From the T_2 distribution at low field, it is possible to indicate one water peak and one oil peak. From the relaxation data (T_1, T_2) it is possible to conclude that T_1 is a better method to decide saturation at high field (200 MHz). At low field (12 MHz) T_2 relaxation is the better option, because T_2 is a more sensitive. From the G_0-T_2 correlation plots it was possible to observe how the internal gradient affected T_2. The T_1-T_2 correlation plots was used to determine the strength of interaction between the surface and the fluid